Sleep disturbances, including insomnia and sleeplessness, are known to affect a vast number of individuals. In addition, many individuals may wish to regulate or control their sleep as a lifestyle choice. Sleep disorders, as well sleep abnormalities symptomatic to a disorder, disease, behavior, or treatment (i.e. sleep issues that occur in response to ADHD treatment, chemotherapy, etc.) affect millions. Moreover, many individuals suffer from sub-clinical or undiagnosed sleep issues that severely affect health and well-being, causing a reduced quality of life. Currently, modulation of sleep and treatment of the symptoms of sleeping disorders is generally accomplished with pharmacological agents. Such agents may be expensive, have associated risk of overdose, and may have undesirable side effects. In addition some people are averse to using drugs to treat seemingly benign conditions such as insomnia and sleeplessness.
It would generally be advantageous to provide apparatuses (devices, systems) and methods for transdermal electrical stimulation for improving sleep. Specifically, there is a need for effective non-drug treatments (or enhancements for existing drug treatments) for sleep.
Described herein are transdermal electric stimulation (hereinafter “TES”) apparatuses (devices and systems) and methods of using them that may be useful in treating sleep. TES (e.g., applied through scalp electrodes) has been used to affect brain function in humans. TES has been shown to improve motor control and motor learning, improve memory consolidation during slow-wave sleep, regulate decision-making and risk assessment, affect sensory perception, and cause movements. TES has been used therapeutically in various clinical applications, including treatment of pain, depression, epilepsy, and tinnitus. Despite the research to date on TES neurostimulation, existing methods and apparatuses for TES are lacking for applications related to the modulation of sleep.
For example, U.S. patent application Ser. No. 13/423,380 titled “DEVICE FOR CONVERTING MUSIC SIGNAL TO ELECTRICAL STIMULATION” by inventor Liang describes systems for adapting music therapy insomnia treatments by converting the analog auditory signal to a time-varying voltage signal delivered to transdermal electrodes targeting acupuncture points. However, audible waveforms of music appropriate for use as a musical therapy intervention for sleep are poorly adapted to transdermal electrical stimulation targeting peripheral nerves. An analog-adapted signal as described by Liang would likely lack high transient peak currents (i.e. pulsing) that may be effective for activating peripheral nerves, and further may be quite uncomfortable due to the presence of significant power in low frequencies (100 s of Hz) without duty cycle limitations.
U.S. patent application Ser. No. 12/616,513, titled “DEEP BRAIN STIMULATION FOR SLEEP AND MOVEMENT DISORDERS” by inventors Wu et al. describes an implantable electrical stimulation system targeting the substantia nigra to treat sleep disorders. The sleep stage of a patient is tracked and stimulation is modulated according to the patient's sleep stage. Such implantable systems have a greater cost and risk relative to noninvasive designs. Further, this invention requires some form of sleep tracking to modulate the applied electrical stimulation. It would be desirable to modulate sleep without requiring such tracking. Similarly, U.S. Pat. No. 8,612,005 to inventors Rezai et al. titled “NEUROSTIMULATION FOR AFFECTING SLEEP DISORDERS” describes another technique for affecting a sleep disorder by stimulating a deep nucleus via an implanted electrode. Another implanted electrical treatment is described in U.S. Pat. No. 5,335,657 to inventors Terry Jr., et al. titled “THERAPEUTIC TREATMENT OF SLEEP DISORDER BY NERVE STIMULATION”. This patent describes an implanted vagal nerve stimulator for treating sleep disorders.
Although non-invasive electrical stimulation devices to treat sleep have been proposed, such devices have not found wide use because they are not effective and/or they result in pain or discomfort during or after use. For example, U.S. Pat. No. 3,648,708 to inventor Haeri titled “ELECTRICAL THERAPEUTIC DEVICE” describes a device to be operated by a medical professional that delivers pulsed or alternating currents at lower frequencies (less than or equal to 250 Hz) for inducing relaxation or sleep. This invention is lacking at least due to the requirement for operation by a medical professional (unsuitability for self-actuation) and limitation to low frequencies that may limit the intensity of stimulation due to discomfort. Discomfort (e.g., due to skin irritation and/or muscle twitching) is believed to decrease with increasing frequency in a range above 250 Hz, thus low-frequency stimulation may be uncomfortable.
Similarly, U.S. Pat. No. 3,255,753 to inventor Wing titled “ELECTRICAL SLEEP MACHINE AND SLEEP INDUCING METHOD” uses a rechargeable battery to power an electrical stimulator and a self-timer as safety features that enable self-operation of the device. The pulses delivered are square pulses, generally less than 40 Hz. Such stimulation is likely to be uncomfortable and/or ineffective for inducing or improving sleep. Discomfort or pain invariably induces physiological arousal in a user and makes falling asleep more difficult.
U.S. Pat. No. 4,418,687 to inventors Matsumoto et al. titled “ELECTRIC SLEEP INDUCER” describes another low frequency (<14 Hz) electrical stimulator for inducing sleep by broadly inhibiting the cerebral cortex. This invention is inspired by the work by Gilyarovsky and colleagues in the mid-19th century that used low (<150 Hz) frequency stimulation to induce sleep.
U.S. Pat. No. 8,029,431 to inventor Tononi et al. titled “METHOD AND APPARATUS FOR PROMOTING RESTORATIVE SLEEP” also operates at brain rhythm (low frequencies), employing magnetic stimulation to entrain brain rhythms at slow-wave (delta) frequencies for enhancing restorative sleep. Such low-frequency magnetic systems may not target peripheral nerves (cranial nerves, vagal nerve, etc.) that can modulate autonomic function and brain state, but may operate under a different regime. Similarly, U.S. patent application Ser. No. 11/025,928 to inventor Wang titled “METHOD FOR MODERATION OF SLEEP DISORDER” describes methods for treating a sleep disorder using a magnetic head acupuncture headgear (see also U.S. Pat. No. 6,280,454 to Wang) for electrical stimulation at 0.3-3.4 kHz using many electrodes implanted on the scalp. These methods require a magnetic material, cap, or a large number of electrode locations making them difficult to operate and apply.
Finally, U.S. Pat. No. 5,792,067 to inventor Karell titled “APPARATUS AND METHOD FOR MITIGATING SLEEP AND OTHER DISORDERS THROUGH ELECTROMUSCULAR STIMULATION” describes a system and method of using an electrode placed on the user's palate or pharynx to mitigate snoring, apnea, etc. As implied by the title, this invention stimulates the muscles, e.g., within the oral cavity, to reduce snoring and/or apnea, and the internal (in the mouth) placement and the energy applied are likely to be uncomfortable, and does not directly modulate sleep (e.g., onset, duration, quality, etc.).
Thus, in general, it would be advantageous to provide apparatuses and methods for transdermal electrical stimulation for improving sleep that are both effective and comfortable for a user.